The invention concerns a process and an arrangement for controlling and regulating a motor with a permanent-magnet rotor with at least one pole pair and one stator with two or more coils. At least one of these coils has driving pulses applied to it. It especially concerns reaction motors of time-keeping devices like watches.
Low-frequency electromagnetically excited stepping switch mechanisms, excited or synchronized oscillating systems, stepping switching motors, and synchronous motors are used as electromechanical converters for timekeeping devices like quartz watches, to transmit the divided quartz frequency to an indicator device. The synchronous motors are driven with the exciter frequency either in a self-starting or in a non-self-starting manner. Such reactive synchronous motors generally have a field coil to which is applied an alternating voltage that is synchronous with the magnetic field generated by the rotational motion of the rotor. Self-starting synchronous motors have the disadvantage of high power consumption. with battery operation, this leads either to frequent battery changes or to a very large battery. Both are undesirable, especially for watches. Besides the disadvantage of high power consumption, self-starting synchronous motors have the further disadvantage that a pulse that has been lost by a pole jump can no longer be recovered. Such a system cannot keep constant the number of revolutions in a given time interval. Non-self-starting motors can no longer start by themselves after a stoppage during operation, but they must be started anew by mechanically cranking the rotor. In addition, in the case of synchronous motors which must be cranked, one must take care that the pointer can be adjusted precisely.
In rotating stepping switching mechanisms (stepping motors), one utilizes the motion of a permanent magnet rotor with n pole pairs in a stator field that is excited through alternating or rectified current pulses by respectively one half or one pole pair step. Stepping switching motors with permanent-magnet rotors have relatively large torque and a high efficiency, due to the high magnetic field, and permit a larger step angle with favorable damping of the step motor. A review of the known solutions can be found in the reference by G. Glaser: "Quartz watch technology" (Wilhelm Kempter KG Publishers, 1979, pages 142-161).
The aim of the present invention is to specify a control and regulation method, as well as an arrangement, according to which a reactive motor with a permanent-magnet rotor will again start up by itself following a stoppage during operation and will, during normal operation, react to a counter-rotational force with an appropriate increase of driving power. At the same time, it will make do with the smallest possible power consumption. Even if the supply voltage has dropped considerably, perfect operation will be assured. Here, the regulation operates with negligible dead time.
According to the invention this aim is achieved by a process which is specified by the features listed in the characteristic part of claim 1.
More extensive features of the inventive control and regulation process are contained in the characteristic parts of claims 2 through 8. An arrangement to perform the inventive control and regulation process is characterized by the features of claim 9.
Further favorable developments of the invention can be taken from claims 10 through 22.
The inventive solution assures self-starting of the motor in a single direction after the motor has stopped or after a considerably reduced rotational speed due to a strong torque at the shaft of the rotor, by switching from nominal running operation to self-starting operation with one or more prescribable frequencies. In normal operation, it guarantees the perfect regulation of the rotational speed of the motor with negligible dead time after the appearance of a counter-torque. Here, the power consumption of the motor in normal operation is exceedingly small and perfect functioning is assured even with a strongly reduced supply voltage. The solution is therefore universally applicable with watches having a small or a large counter-torque, i.e. for small wristwatches or table clocks up to large wall clocks.